Pretensioned contact springs for pushbottom consoles

ABSTRACT

A pretensioned contact switch includes alternate long and short contact springs that have first legs partially embedded in corresponding parallel aligned slots of a plastic insulating base and secured therein. A first plastic stop affixed to and protruding from the base abuts a tab extending down from a second leg of the short contact spring to tension the short contact spring. A second plastic stop affixed to and protruding from the base abuts against a second leg of the long contact spring to place the long contact spring in tension. Pushbutton-actuated means move the second leg of the long contact spring away from the second plastic stop toward the second leg of the short contact spring to close the contact switch.

United" States Patent [72] inventor [21 Appl. No. [22] Filed [45Patented [73] Assignee 54 PRETENSIONED CONTACT SPRINGS FOR PUSHBU'I'IONCONSOLES 9 Claims, 10 Drawing Figs. [52] U.S.Cl..' 200/166, v 200/ l 59,200/5 [51] Int. Cl 1101b 1/50 [50] Field otSearch ZOO/166.1, 159A, 159,53, SD, SE, l66l-l(cursory), 164

[56] References Cited UNITED STATES PATENTS 2,231,365 2/1941 Matthews eta1 200/5(E) 2,823,271 2/1958 Wagstaff 200/166(.1)X 2,864,900 12/1958Simmons 200/166(.1)X 4 2,970,200 1/1961 Walker etal. 200/l66(.1)

3,355,558 11/1967 Geese et al. 200/5(E) 3,392,250 7/1968 Ziegler et al200/159 FOREIGN PATENTS 1,074,124 6/1957 Germany 200/ 166(. 1) 1,084,3476/1960 Germany ZOO/159 1,186,935 2/1965 Germany 200/l66(. 1)

Primary Examiner-Robert K. Schaefer Assistant Examiner-Robert A.Vanderhye Attorneys-H. J. Winegar, R. P. Miller and A. J. NugentABSTRACT: A pretensioned contactswitch includes altemate long and shortcontact springs that have first-legs par tially embedded incorresponding parallel aligned slots of a plastic insulating base andsecured therein. A first plastic stop affixed to and protruding from thebase abuts a tab extending down from a second leg of the short contactspring to tension the short contact spring. A second plastic stopaffixed to and protruding from the base abuts against a second leg ofthe long contact spring to place the long contact spring in tension.Pushbutton-actuated means move the second leg of the long contact springaway from the second plastic stop toward the second leg of the shortcontact spring to close the contact switch.

PATENTED JAN26 |97| SHEET 2 [IF 3 PRETENSIONED CONTACT SPRINGS FORPUSHBUTTON CONSOLES BACKGROUND OF THE INVENTION I Field ofthe InventionThis invention is drawn to pushbutton-actuated switches for connecting,e.g., telephone lines to a telephone console, and more particularly toswitches of this type having pretensioned contact spring sets.

2. Discussion Sets of contact spring elements are generally employed inswitches having particular utility in telephone console sets, wherein apushbutton may be selectively actuated to cause lateral movement of theelements with respect to each other to open or close a circuit. In theoperation of these switches it is necessary that the spring element moveprecise distances, and that actual movement should occur only uponactuation of the pushbutton means.

It has been found that the reliability of contact spring operation inthese consoles can be enhanced by pretensioning the springs againstfixed stops or elements so as to insure that the contact springs arealways returned to a predetermined position following restoration of thepushbutton to a line disconnect position. For example, in U. S. Pat. No.3,271,530 issued Sept. 6, I966 to a R. E. Wirsching, there is shown apushbutton-controlled switch for a telephone console having pretensionedcontact spring pairs wherein one contact spring of each pair ispretensioned against a stop and the other contact spring is pretensionedagainst a cam element formed on the pushbutton. However, thisconstruction necessitates the formation of special cams on eachpushbutton for operating each pair of contact springs.

It would be advantageous to mount the contact springs, the cams, and thepushbuttons in a unitary assembly and to eliminate the need for aretaining plate to hold the pushbuttons in the housing; and, inaddition, to eliminate the need for a series of separate cams affixed toa single pushbutton to aid in the pretensioning of the contact springsin the switch.

SUMMARY OF THE INVENTION The present invention is drawn to a switchassembly for mounting, pretensioning, and moving contact springs in sucha manner that these advantageous features are obtained. The need forretaining plates to secure the pushbutton to the terminal housing isobviated by integrally forming a plurality of cavities on the top partof the terminal housing for containing the pushbutton. Apertures areformed within the cavities and extend in a desired relationship throughthe base of the housing to provide access means for actuating thecontact springs by means of the pushbuttons. Alternate long and shortcontact springs constitute a contact pair, and a desired number ofcontact pairs making up a switch are mounted in corresponding slots onthe base of the housing. In addition, a plurality of protruding plasticstops are affixed in a desired arrangement on the base of the housing toflex or pretension all the first contact springs and the outer one ofthe second contact springs of each switch. A necked-down spacer isinserted through openings formed in the intermediate second contactsprings and pass through so as to abut the sides of the correspondinginner and outer second contact springs to transfer the pretension of theouter second contact spring to the other second contact springs, therebyeffecting pretension to the entire switch. Thus, a plurality of cams areno longer directly used for pretensioning the second contacts of eachswitch. A single plunger located within each aperture of the housing andin engaging relation with the pushbutton is situated so as to movedownward upon actuation out of the base of the housing into engagingrelationship with an inwardly bent tab extending from the outer secondcontact member, thereby causing a lateral movement of the second contactmember up and away from the pretensioning stop. This movement istransferred to the other second contacts by means of the necked-downspacer and also is transferred to the first contact members.

Thus, the contact pairs of a switch move simultaneously as a unit in asingle direction away from the pretensioning stops to close the switch.

DESCRIPTION OF THE DRAWINGS A more complete understanding of theinvention and its advantages will appear more fully from the followingdetailed description taken in conjunction with the appended drawings,wherein:

FIG. I is a rear view of a multipushbutton switch assembly modified toinclude a pretensioned switch employing the present invention;

FIG. 2 is a fragmentary bottom view of the pretensioned switch,embodying certain features of the invention;

FIG. 3 is an exploded perspective view of a portion of an insulatingterminal base of the switch assembly, illustrating the specific mannerin which a typical pair of contact springs are mounted in the terminalbase;

FIG. 4 is a perspective view showing additional features of the terminalbase and two sets of pretensioned contact spring members fixed thereon;

FIG. 5 is a side view of a long contact spring member employed in thearrangement of FIG. 4;

FIG. 6 is a side view of a short contact spring member employed in thearrangement of FIG. 4;

FIG. 7 is a cut away side view of a pushbutton unit which may be used tooperate the switch assembly shown in FIG. I, the unit being shown in acondition to be inserted into the base;

FIG. 8 is a fragmentary side view, in section, taken along the line 8-8of FIG. 1, illustrating the pushbutton unit of FIG. 1 in its assembledposition within the base;

FIG. 9 is an exploded perspective view of the pushbutton unitillustrating the relationship of a button and a collar therein; and

FIG. 10 is a fragmentary perspective view of a block with a modifiedsquare cross-sectional plunger and a square crosssectional stop forpretensioning a long contact spring.

DETAILED DESCRIPTION Referring now more particularly to the drawing,FIG. 1 shows a unitary console housing 9, having a plurality ofpushbuttons l0 mounted on the top thereof. The pushbuttons are inengaging relationship with respective underlying lockout cams llsituated in the housing 9. Each respective lockout cam is situated justabove one of a plurality of switches 12-17 that constitute the subjectof the invention. The lockout cams are identical to the cams shown inthe previously discussed Wirsching patent. When one of the switches(illustratively 15) is closed, the remaining switches l2-l4 and l6-l8are open, and the open switches are locked out by the associated earns11.

The housing 9 consists of a a molded plastic block 18 that carries thepushbuttons l0 and the cams l1, and b an elongated base 18A having abottom surface 188 on which the switches l2-1'7 are mounted. Base 18Ahas a top surface 18C (FIG. 3) that protrudes from the bottom of theblock 18 (FIG. 4). A plurality of axially spaced transverse slots19A-19B, one pair of which are shown, are disposed in a sidewall 18D andthe adjacent top and bottom walls 18C and 188, respectively, of the base18A.

Each pair of slots 19A and 19B receive an associated pair of relativelylong and relatively short planar contact springs 22 and 23,respectively. As indicated below, any desired number of pairs of contactsprings 22 and 23 may be employed in each of the switches 12l7 (FIG. 1).

As best shown in FIG. 5, each long contact spring 22 is basically anL-shaped, flat or planar metal sheet which can be easily flexed. Inparticular, each spring 22 includes a contact leg 24 which has aprecious metallic contact point 26 afiixed to and protruding from onesurface. Extending downward from contact leg 24 is an anchoring leg 27which carries a laterally projecting seating portion 28 and terminatesin a terminal portion 29. Each short contact spring 23 (FIG. 6), whichis a flat metal sheet like the long spring 2 2 (FIG. 5), includes acontact leg 32 (FIG. 6) which carries a stop tab 36. A precious metalliccontact point 33 is affixed to and protrudes from one surface of thecontact leg 32 in a direction opposite to that of the contact point 26(FIG. 5). An anchoring leg 34 (FIG. 6) extends downward from contact leg32 and carries an L-shaped terminal leg 37 having a lateral seatingportion 37A and a vertical terminal portion 38. As best shown in FIG. 3,contact leg 32 of short contact spring 23 is shorted than contact leg 24of long contact spring 22.

'The long contact spring 22 is positioned such that the anchoring leg 27rests in the portion of the slot 19B disposed on the side surface 18D ofthe base 18A, while the laterally extending portion 28 rests in theportion of the slot 198 disposed in the top surface 18C (FIG. 3). Theshort contact spring 23 is placed in the slot 19A such that theanchoring leg 34 is parallel to the anchoring leg 27 of the contactspring 22 and the laterally extending portion 37 of spring 23 isparallel to the laterally extending portion 28 of the spring 22. Thedimerisions of the springs 22 and 23 are chosen such that l)th e contactlegs 24 and 32 are spaced from the bottom surface 18B (FIG. 4) of thebase 18A, and (2)t he terminal leg 29 extends upwardly from the topsurface 18C and flush with the sidewall 18D while the terminal leg 38extends upwardly from an interr'n'ediate portion of the top wall 18C(FIG. 3), for reasons to be explained later. Cement sealer 30 (FIG; 4)is placed between terminal legs 29 and 38 to embed the springs withinthe base 18A. Contact'leg 24 and the contact leg 32 are so arranged thatcontact point 26 and contact point 33 are situated 0pposite each other.

Long contact spring 22 and an adjacent short contact spring a 23 mountedas shown in FIG. 3 constitute a single contact pair. A plurality (e.g.,three) of such contact pairs make up each of the switches l217 (FIG. 1)with the contact pair's designated 22A-23A, 228-238, and 22C-23C in FIG.4 making up the switch to be described in more detail below.

A cylindrical bore 39 (FIG. 2) extends through the base 18 adjacent thelong contact spring 22A. The center of the bore spaced from the spring22A, while -a portion of the bore periphery underlies the contact leg 24on spring 22A as shown. A pushbutton operated cylindrical plunger 40 isslidably mounted within the bore 39 and is provided with a beveled tip41 which is extendible in a direction but of the drawing as viewed inFIG. 2. The contact leg 24 on the long spring 22A carries an actuatortab 42 for selective engage ment with the underlying tip 41 of theplunger 40. The tab 42 is partially bent under so that an upward forceapplied thereto will tend to move the leg 24 to the left as viewed inFIG. 4. i

A stop 46 having an arcuate guideway 47 extends upwardly from theperipheral wall of the bore 39 for guiding the plunger 41 when thelatter is extended out of the base 18A. The stop 46 has a side 47A (FIG.2) in engagement with an upper por tion of the contact leg 24 on thespring 22A. The side 47A is interposed in the path of a rectilinear axisof the leg 24 to flex, or pretension, the leg 24 as viewed in FIG. 2.

The contact leg 24 of the intermediate long spring 228 is provided withan opening 43 for receiving a necked-down spacer 44 laterallytherethrough. The larger portion of the spacer abuts the contact leg 24of the long spring 22A and the smaller portion of the spacer abuts thecontact leg 24 of the long spring 22C. As a consequence, the pretensionimparted on to the contact leg 24 of the long contact spring 22A by thestop 46 is transmitted to the contact legs 24 of the remaining longcontact springs 22B and 22C of the switch 15 by way of the necked-downspacer 44.

A plurality of additional, but smaller protruding plastic stops 48,which are spaced on the bottom surface 183 of the base 18 (FIG. 4), arerespectively situated under the contact legs 32 of each of the shortercontact springs 23A, 23B, 23C to engage the stop tabs 36 thereon. Therespective stops 48 are interposed in the paths of the rectilinear axesof the contact legs 32 to pretension the contact legs 32 and to normallyflex each contact leg 32 away from each contact leg 24. Thus, thenecked-down spacer 44, the stop 46, and the stops 48 cooperate to effecta pretension on all of the spring contacts 22, 23 of the switch 15.

As shown in FIG, 1, FIG. 2, and FIG. 7, the plunger 40 of the switch 12extends vertically through the bore 39 in the base 18A and through analigned bore 48A in the block 18. A recessed surface 49 (FIG. 7) in theblock 18 terminates a bore 50 which communicates with the bore 48A andreceives an individual pushbutton 10. As best shown in FIG. 9, thepushbutton 10 includes a hollow square plastic collar 51 provided withslots 53 and 54 at two corners to from a flexible tab 56. On this tab 56at the base of the collar 51, a pair of opposed, outwardly extendinglips 57-57 are formed. As shown in FIG. 7. the lips 57 are receivablewithin a pair of opposed grooves 58-58 disposed within a wall portion 59of the block 18 adjacent the recessed surface 49. A plastic rectangularbutton 52 having an extended rim 62 (FIG. 9) around one end is designedto fit within the collar 51 and projects outward therefrom. Acorresponding recessed shoulder 63 formed within the collar 51 isdesigned to abut the rim 62 of the button 52. Thus, the button 52 isdesigned to'be in sliding engagement within the collar 51, with theshoulder 63 preventing the button 52 from sliding completely through thecollar 51. The button 52 is inserted into the collar 51 in a manner asillustrated in- FIG. 9 prior to the insertion of the collar into theblock 18 (FIG. 7). i

The manner of inserting the pushbutton 10 into the bloc I8 is shown inFIG. 7. Sufficient inward. pressure is exerted on the flexible tab 56 sothat the lips 57 are jflexed inward toprovide enough clearance to passinto the bore 50 and snap into position in the grooves 58. The finalposition is shown in FIG. 8. In this position, the bottom surface ofth'e button 52 is in engaging relation with the plunger 40.

It will be noted from FIGS. 2, 3, and 4 that the terminal. legs 29 ofthe long contact spring member 22 and the terminal legs 38 of the shortcontact spring member 23, when assembled, are at an offset staggeredrelationship. This was designed so that the terminals 29 and 38 of theswitches are spaced apart to facilitate the connection of outgoing wires(not shown) to the switches.

The operation of, the exemplary switch 15 (FIG. 1) in the pushbuttonconsole will now bedescribed. When the button 52 is depressed, theplunger 40 is forced downward against the force of the locking carn 11,so thatthe plunger is projected out of the bore 39 through the bottom ofthe base 18. This downward movement is guided and backed up by thearcuate, crescent-shaped side 47 (FIG. 4) of the plastic protruding stop46. As the plunger moves out of the bore 39, it contacts the bent inwardtab 4 2carriedby contact leg 24 of the outer long contact spring member22A to cam the contact leg 24 diagonally up and laterally away fromplastic stop 46. The beveled tip 41 of the plunger slides congruentlywith the bent tab 42 as the lateral-movement takes place and therebyfacilitates this movement. I

Due to the presence of the necked-down spacer 44, the contact leg 24 ofthe inner long contact springs 22B and 22C move simultaneously with theouter long contact spring 22A. Also, the lateral thrust of the contactlegs 24 overcomes the restraint imposedby the spacers 48 on thedownwardly extending portions 37 of the contact legs 32 of the shortcontact.

springs 23A, 23B and 23C, andsimultaneously forces the lateral movementof the contact legs 24 to be imparted to the contact legs 32. Thus, thecontact legs 24 and32are moved away from their respective stops 46 and48 in a single, unitary motion, enabling contact points 26 and 33 toengage. The upward lateral movement imparted to the contact legs 24 as aresult of the engagement of the inwardly bent tab 42 by the plunger 41enables each contact leg 24 to clear stops 48 when,

engaging a respective contact leg 32 as shown in FIGS. 2 and 4. Theupward, lateral unitary movement also insures good wiping contactbetween c'ontact points 26 and 33. The cumulative engagement of contactpoints 26 of contact spring members 22A, 22B, and 22C with the contactpoints 33 of contact spring members 23A, 23B, and 23C acts to close theswitch as illustrated in FIG. 4. The other switches l2l4, l6, and 17(FIG. 1) remain open due to the synchronous action of the locking cams11, the mechanism of which is well known in the art and explained indetail in the previously referred to Wirsching patent.

With this operation, the contact spring members are constantly undertension, and furthermore, are able to move laterally with respect toeach other in one direction in order to open or close a circuit.Moreover, it is now possible with this invention to house a pushbuttonswitch console in a single unitary housing.

A modified switch structure with pretensioned. contact springs is shownin H6. 10. A square bore 139 extends through the base 18A adjacent thelong contact spring 22A. As shown, a portion of the bore peripheryunderlies the actuator tab 42 of the spring 22A, whereas the remainingportion is spaced therefrom. A square plunger 140 having flat sides anda cam shaped or arcuate tip 141 is slidably mounted within the bore 139.The other end of the plunger 140 is in engaging relation with apushbutton assembly.

A stop 146 having flat sides 147 and 147A extends up from the peripheralwall of the bore 139. The flat side 147 acts as a guideway for thesquare plunger 140 and the side 147A is interposed in the path of therectilinear axis of the contact spring 22A to flex the contact leg 24.

As the plunger 140 is projected from the bore 139 of the base 18A, itcomes into engaging relationship with the flat side 147 of stop 146. Asthe downward ,movementprogresses, the cam tip 141 of the plunger engagesbent tab 42, which flexes the contact leg 24 away from stop 146. Oneflat side of the plunger slides congruently and is guided by the flatside 147 of the stop 146, thereby preventing any twisting of the plungerduring this downward movement.

The rest of the assembly is identical to that shown in FIGS. 1, 2, and4, and the operation of the switch is essentially that as disclosed withreference to FIG. 2.

The above-described pushbutton switch device illustrates the principlesof the present invention. Modifications in the device may be made bypersons skilled in' the art without departing from the scope of thepresent invention.

lclaim:

l. A pretensioned contact spring switch, comprising:

an insulating base having a bottom surface;

a switch set connected to said base comprising inner, intermediate, andouter contact par pairs disposed successively along said bottom surface,each contact pair having a long contact spring and an adjacent shortcontact spring;

a series of first protruding stops affixed to said bottom surface andinterposed in the axial path of an engaging "each short spring to flexsaid short spring outwardly and away from the adjacent long spring inthe associated pair;

an elongated necked-down spacer projecting transversely through the longspring of the intermediate pair and abutting the long springs of theouter and inner pairs to gang said long springs together,

a second protruding stop affixed to said bottom surface and interposedin the axial path of and engaging the long spring of the inner pair toflex said spring toward the flexed inner short spring, said first stopsnormally preventing contact between the adjacent long and short springsof the respective pairs; and

means provided within the base for moving said inner long spring awayfrom said second stop and into engaging relationship with the shortspring in the associated pair, the movement of the inner long springbeing transmitted to the outer long springs in the switch through thespacer to move the intermediate and the outer long springs into engagingrelation with the associated short springs.

2. A pretensioned contact spring set comprising:

an elongated insulating base having a pair of substantially parallelslots formed in along edge thereof;

a pair of alternate long and short contact spring members connected tosaid base;

each of said alternate long and short contact members comprising ananchor section, a terminal leg, and a contact g;

each anchor section embedded incorresponding slots of said base; V I

each terminal leg extending downward from a bottom side of said base;

each contact leg projecting over and spaced from a top side of saidbase, the contact leg of said short contact member having a straight tabextending downward and the contact leg of said long member having aninwardly bent tab extending downward;

a first protruding stop on said top side of said base, situated betweensaid contact members, and engaging said tab of said short contact memberto tension said short contact member;

a second protruding stop affixed to said top side of said base andengaging the outer side of the contact leg of said long contact memberto tension said long contact member;

and

means for moving said long contact leg toward said short contact leg.

3. The set as set forth in claim 2, wherein said base has a cavity,located beneath said bent tab of said long contact member, for receivingsaid moving means. i

4. The set as set forth inclaim 3, wherein said moving means is akey-operated plunger situated within the cavity, and having a cam facefor engaging said bent tab.

5. In a pretensioned contact set assembly:

a block having a polygonal cross section, said block having a pair ofslots extending into one side of said block;

a first contact spring member having an anchor section mounted in afirst of said slots and a right angular first contact leg extending overand spaced from an adjacent side of said block, said contact leg havinga depending tab extending toward, but spaced from, said adjacent side;

a first stop extending from said adjacent side for engaging said tab andflexing said first contact leg;

a second contact spring member having an anchor section mounted in thesecond of said slots, and a right angular section second contact legextending over and spaced from said adjacent side of said block with theunderside of said second contact leg spaced to clear the top of thefirst stop;

a second stop extending from said adjacent side of said block forengaging an end portion of said second contact leg and flexing saidsecond contact leg toward the first contact leg; and

means for moving said second contact leg away from the second stop tomove the underside of said second contact leg over the first stop.

6. In a switch unit:

a unitary block having a plurality of spaced stops projecting from onesurface thereof;

a plurality of pairs of L-shaped contact springs each having an anchorsection and a contact leg;

means for securing the anchor section of one of each pair of contactsprings to a side of said block with the contact leg extending over anadjacent side of said block to engage and be flexed against one of saidstops;

means for securing the anchor section of only a predetermined one of theremaining contact springs to said side of said block with its contactleg extending over said adjacent side of said block to engage and beflexed against one of said stops;

means for securing the anchor sections of the other remaining contactsprings to said side of said block with their contact legs extendingover said adjacent side of block; and

means rendered effective by the flexing of the leg of the predeterminedcontact spring for flexing the legs of the cither remaining contactsprings.

7. In a pushbutton operated switch:

a housing having a bore extending therethrough;

a plunger slidably mounted in said bore;

a stop affixed to and extending from the housing with a guide surfacealigned with said bore and conforming in shape to a portion of theplunger;

a contact spring attached to the housing and flexed against a side ofthe stop;

a tab extending from said contact spring overlying said bore to beengaged by the plunger; and

a button engaging said plunger for sliding said plunger through saidbore and along said guide surface to act on

1. A pretensioned contact spring switch, comprising: an insulating basehaving a bottom surface; a switch set connected to said base comprisinginner, intermediate, and outer contact par pairs disposed successivelyalong said bottom surface, each contact pair having a long contactspring and an adjacent short contact spring; a series of firstprotruding stops affixed to said bottom surface and interposed in theaxial path of an engaging each short spring to flex said short springoutwardly and away from the adjacent long spring in the associated pair;an elongated necked-down spacer projecting transversely through the longspring of the intermediate pair and abutting the long springs of theouter and inner pairs to gang said long springs together, a secondprotruding stop affixed to said bottom surface and interposed in theaxial path of and engaging the long spring of the inner pair to flexsaid spring toward the flexed inner short spring, said first stopsnormally preventing contact between the adjacent long and short springsof the respective pairs; and means provided within the base for movingsaid inner long spring away from said second stop and into engagingrelationship with the short spring in the associated pair, the movementof the inner long spring being transmitted to the outer long springs inthe switch through the spacer to move the intermediate and the outerlong springs into engaging relation with the associated short springs.2. A pretensioned contact spring set comprising: an elongated insulatingbase having a pair of substantially parallel slots formed in a long edgethereof; a pair of alternate long and short contact spring membersconnected to said base; each of said alternate long and short contactmembers comprising an anchor section, a terminal leg, and a contact leg;each anchor section embedded in corresponding slots of said base; eachterminal leg extending downward from a bottom side of said base; eachcontact leg projecting over and spaced from a top side of said base, thecontact leg of said short contact member having a straight tab extendingdownward and the contact leg of said long member having an inwardly benttab extending downward; a first protruding stop on said top side of saidbase, situated between said contact members, and engaging said tab ofsaid short contact member to tension said short contact member; a secondprotruding stop affixed to said top side of said base and engaging theouter side of the contact leg of said long contact member to tensionsaid long contact member; and means for moving said long contact legtoward said short contact leg.
 3. The set as set forth in claim 2,wherein said base has a cavity, located beneath said bent tab of saidlong contact member, for receiving said moving means.
 4. The set as setforth in claim 3, wherein said moving means is a key-operated plungersituated within the cavity, and having a cam face for engaging said benttab.
 5. In a pretensioned contact set assembly: a block having apolygonal cross section, said block having a pair of slots extendinginto one side of said block; a first contact spring member having ananchor section mounted in a first of said slots and a right angularfirst contact leg extending over and spaced from an adjacent side ofsaid block, said contact leg having a depending tab Extending toward,but spaced from, said adjacent side; a first stop extending from saidadjacent side for engaging said tab and flexing said first contact leg;a second contact spring member having an anchor section mounted in thesecond of said slots, and a right angular section second contact legextending over and spaced from said adjacent side of said block with theunderside of said second contact leg spaced to clear the top of thefirst stop; a second stop extending from said adjacent side of saidblock for engaging an end portion of said second contact leg and flexingsaid second contact leg toward the first contact leg; and means formoving said second contact leg away from the second stop to move theunderside of said second contact leg over the first stop.
 6. In a switchunit: a unitary block having a plurality of spaced stops projecting fromone surface thereof; a plurality of pairs of L-shaped contact springseach having an anchor section and a contact leg; means for securing theanchor section of one of each pair of contact springs to a side of saidblock with the contact leg extending over an adjacent side of said blockto engage and be flexed against one of said stops; means for securingthe anchor section of only a predetermined one of the remaining contactsprings to said side of said block with its contact leg extending oversaid adjacent side of said block to engage and be flexed against one ofsaid stops; means for securing the anchor sections of the otherremaining contact springs to said side of said block with their contactlegs extending over said adjacent side of block; and means renderedeffective by the flexing of the leg of the predetermined contact springfor flexing the legs of the other remaining contact springs.
 7. In apushbutton operated switch: a housing having a bore extendingtherethrough; a plunger slidably mounted in said bore; a stop affixed toand extending from the housing with a guide surface aligned with saidbore and conforming in shape to a portion of the plunger; a contactspring attached to the housing and flexed against a side of the stop; atab extending from said contact spring overlying said bore to be engagedby the plunger; and a button engaging said plunger for sliding saidplunger through said bore and along said guide surface to act on saidtab to flex said contact spring away from said stop.
 8. In a pushbuttonoperated switch as defined in claim 7, wherein the plunger iscylindrical in shape, and the stop has an arcuate surface which guidesand backs up the plunger upon operation of the pushbutton.
 9. In apushbutton operated switch as defined in claim 7, wherein the plunger issquare in cross-sectional configuration, and said plunger has a flatsurface which slides along a flat surface of said stops to precludetwisting of the plunger upon operation of the pushbutton.